New GoTags improvements

* Use new `gomodifytags` tool to manipulate and modify tags
* Adds new `:GoRenameTags`
* `:GoAddTags` is able to add options
* `:GoRemoveTags` is able to remove options

Usage:

Following command add multiple tags. Does not modify if the key already
exist. If `,optionaname` is given, it adds the given option to that key.
If called without arguments, it adds by default tags with `json` key.
```
:GoAddTags
:GoAddTags json
:GoAddTags json,omitempty
:GoAddTags json hcl bson
:GoAddTags json,omitempty hcl bson
```

Following command removes multiple tags and options. If `,optionname` is
given, it removes the option belonging to that key instead of removing
the key. If called without arguments, it removes all tags belonging to a
struct.

```
:GoRemoveTags
:GoRemoveTags json
:GoRemoveTags json,omitempty
:GoRemoveTags json hcl bson
:GoRemoveTags json,omitempty hcl bson
```

Fixes following issues:

 #984
 #985
 #990
 #1064
 #1091

autoload/go/tags.vim

@@ -0,0 +1,206 @@
+function! go#tags#Add(start, end, count, ...) abort
+  let fname = fnamemodify(expand("%"), ':p:gs?\\?/?')
+  if &modified
+    " Write current unsaved buffer to a temp file and use the modified content
+    let l:tmpname = tempname()
+    call writefile(getline(1, '$'), l:tmpname)
+    let fname = l:tmpname
+  endif
+
+  let offset = 0
+  if a:count == -1 
+    let offset = go#util#OffsetCursor()
+  endif
+
+  let test_mode = 0
+  call call("go#tags#run", [a:start, a:end, offset, "add", fname, test_mode] + a:000)
+
+  " if exists, delete it as we don't need it anymore
+  if exists("l:tmpname")
+    call delete(l:tmpname)
+  endif
+endfunction
+
+function! go#tags#Remove(start, end, count, ...) abort
+  let fname = fnamemodify(expand("%"), ':p:gs?\\?/?')
+  if &modified
+    " Write current unsaved buffer to a temp file and use the modified content
+    let l:tmpname = tempname()
+    call writefile(getline(1, '$'), l:tmpname)
+    let fname = l:tmpname
+  endif
+
+  let offset = 0
+  if a:count == -1 
+    let offset = go#util#OffsetCursor()
+  endif
+
+  let test_mode = 0
+  call call("go#tags#run", [a:start, a:end, offset, "remove", fname, test_mode] + a:000)
+
+  " if exists, delete it as we don't need it anymore
+  if exists("l:tmpname")
+    call delete(l:tmpname)
+  endif
+endfunction
+
+" run runs gomodifytag. This is an internal test so we can test it
+function! go#tags#run(start, end, offset, mode, fname, test_mode, ...) abort
+  " do not split this into multiple lines, somehow tests fail in that case
+  let args = {'mode': a:mode,'start': a:start,'end': a:end,'offset': a:offset,'fname': a:fname,'cmd_args': a:000}
+
+  let result = s:create_cmd(args)
+  if has_key(result, 'err')
+    call go#util#EchoError(result.err)
+    return -1
+  endif
+
+  let command = join(result.cmd, " ")
+
+  call go#cmd#autowrite()
+  let out = go#util#System(command)
+  if go#util#ShellError() != 0
+    call go#util#EchoError(out)
+    return
+  endif
+
+  if a:test_mode
+    exe 'edit ' . a:fname
+  endif
+
+  call s:write_out(out)
+
+  if a:test_mode
+    exe 'write! ' . a:fname
+  endif
+endfunc
+
+
+" write_out writes back the given output to the current buffer
+func s:write_out(out) abort
+  " not a json output
+  if a:out[0] !=# '{'
+    return
+  endif
+
+  " nothing to do
+  if empty(a:out) || type(a:out) != type("")
+    return
+  endif
+
+  let result = json_decode(a:out)
+  if type(result) != type({})
+    call go#util#EchoError(printf("malformed output from gomodifytags: %s", a:out))
+    return
+  endif
+
+  let lines = result['lines']
+  let start_line = result['start']
+  let end_line = result['end']
+
+  let index = 0
+  for line in range(start_line, end_line)
+    call setline(line, lines[index])
+    let index += 1
+  endfor
+endfunc
+
+
+" create_cmd returns a dict that contains the command to execute gomodifytags
+func s:create_cmd(args) abort
+  if !exists("*json_decode")
+    return {'err': "requires 'json_decode'. Update your Vim/Neovim version."}
+  endif
+
+  let bin_path = go#path#CheckBinPath('gomodifytags')
+  if empty(bin_path)
+    return {'err': "gomodifytags does not exist"}
+  endif
+
+  let l:start = a:args.start
+  let l:end = a:args.end
+  let l:offset = a:args.offset
+  let l:mode = a:args.mode
+  let l:cmd_args = a:args.cmd_args
+
+  " start constructing the command
+  let cmd = [bin_path]
+  call extend(cmd, ["-format", "json"])
+  call extend(cmd, ["-file", a:args.fname])
+
+  if l:offset != 0
+    call extend(cmd, ["-offset", l:offset])
+  else
+    let range = printf("%d,%d", l:start, l:end)
+    call extend(cmd, ["-line", range])
+  endif
+
+  if l:mode == "add"
+    let l:tags = []
+    let l:options = []
+
+    if !empty(l:cmd_args)
+      for item in l:cmd_args
+        let splitted = split(item, ",")
+
+        " tag only
+        if len(splitted) == 1 
+          call add(l:tags, splitted[0])
+        endif
+
+        " options only
+        if len(splitted) == 2 
+          call add(l:tags, splitted[0])
+          call add(l:options, printf("%s=%s", splitted[0], splitted[1]))
+        endif
+      endfor
+    endif
+
+    " default value
+    if empty(l:tags)
+      let l:tags = ["json"]
+    endif
+
+    " construct tags
+    call extend(cmd, ["-add-tags", join(l:tags, ",")])
+
+    " construct options
+    if !empty(l:options)
+      call extend(cmd, ["-add-options", join(l:options, ",")])
+    endif
+  elseif l:mode == "remove"
+    if empty(l:cmd_args)
+      call add(cmd, "-clear-tags")
+    else
+      let l:tags = []
+      let l:options = []
+      for item in l:cmd_args
+        let splitted = split(item, ",")
+
+        " tag only
+        if len(splitted) == 1 
+          call add(l:tags, splitted[0])
+        endif
+
+        " options only
+        if len(splitted) == 2 
+          call add(l:options, printf("%s=%s", splitted[0], splitted[1]))
+        endif
+      endfor
+
+      " construct tags
+      if !empty(l:tags)
+        call extend(cmd, ["-remove-tags", join(l:tags, ",")])
+      endif
+
+      " construct options
+      if !empty(l:options)
+        call extend(cmd, ["-remove-options", join(l:options, ",")])
+      endif
+    endif
+  else
+    return {'err': printf("unknown mode: %s", l:mode)}
+  endif
+
+  return {'cmd': cmd}
+endfunc

autoload/go/tags_test.vim

@@ -0,0 +1,30 @@
+func Test_add_tags()
+  let input_file = tempname()
+  call writefile(readfile("test-fixtures/tags/add_all_input.go"), input_file)
+
+  let expected = join(readfile("test-fixtures/tags/add_all_golden.go"), "\n")
+
+  " run for offset 40, which is inside the struct
+  call go#tags#run(0, 0, 40, "add", input_file, 1)
+
+  let actual = join(readfile(input_file), "\n")
+
+  call assert_equal(expected, actual)
+endfunc
+
+
+func Test_remove_tags()
+  let input_file = tempname()
+  call writefile(readfile("test-fixtures/tags/remove_all_input.go"), input_file)
+
+  let expected = join(readfile("test-fixtures/tags/remove_all_golden.go"), "\n")
+
+  " run for offset 40, which is inside the struct
+  call go#tags#run(0, 0, 40, "remove", input_file, 1)
+
+  let actual = join(readfile(input_file), "\n")
+
+  call assert_equal(expected, actual)
+endfunc
+
+

autoload/go/test-fixtures/tags/add_all_golden.go

@@ -0,0 +1,16 @@
+package main
+
+type Server struct {
+	Name          string   `json:"name"`
+	ID            int      `json:"id"`
+	MyHomeAddress string   `json:"my_home_address"`
+	SubDomains    []string `json:"sub_domains"`
+	Empty         string   `json:"empty"`
+	Example       int64    `json:"example"`
+	Example2      string   `json:"example_2"`
+	Bar           struct {
+		Four string `json:"four"`
+		Five string `json:"five"`
+	} `json:"bar"`
+	Lala interface{} `json:"lala"`
+}

autoload/go/test-fixtures/tags/add_all_input.go

@@ -0,0 +1,16 @@
+package main
+
+type Server struct {
+	Name          string
+	ID            int
+	MyHomeAddress string
+	SubDomains    []string
+	Empty         string
+	Example       int64
+	Example2      string
+	Bar           struct {
+		Four string
+		Five string
+	}
+	Lala interface{}
+}

autoload/go/test-fixtures/tags/remove_all_golden.go

@@ -0,0 +1,16 @@
+package main
+
+type Server struct {
+	Name          string   
+	ID            int      
+	MyHomeAddress string   
+	SubDomains    []string 
+	Empty         string   
+	Example       int64    
+	Example2      string   
+	Bar           struct {
+		Four string 
+		Five string 
+	} 
+	Lala interface{} 
+}

autoload/go/test-fixtures/tags/remove_all_input.go

@@ -0,0 +1,16 @@
+package main
+
+type Server struct {
+	Name          string   `json:"name"`
+	ID            int      `json:"id"`
+	MyHomeAddress string   `json:"my_home_address"`
+	SubDomains    []string `json:"sub_domains"`
+	Empty         string   `json:"empty"`
+	Example       int64    `json:"example"`
+	Example2      string   `json:"example_2"`
+	Bar           struct {
+		Four string `json:"four"`
+		Five string `json:"five"`
+	} `json:"bar"`
+	Lala interface{} `json:"lala"`
+}

ftplugin/go/commands.vim

@@ -14,14 +14,15 @@ command! -range=% GoChannelPeers call go#guru#ChannelPeers(<count>)
 command! -range=% GoReferrers call go#guru#Referrers(<count>)
 command! -nargs=? GoGuruTags call go#guru#Tags(<f-args>)
 
-
-command! -nargs=* -range GoAddTags call go#util#AddTags(<line1>, <line2>, <f-args>)
-
 command! -range=0 GoSameIds call go#guru#SameIds()
 command! -range=0 GoSameIdsClear call go#guru#ClearSameIds()
 command! -range=0 GoSameIdsToggle call go#guru#ToggleSameIds()
 command! -range=0 GoSameIdsAutoToggle call go#guru#AutoToogleSameIds()
 
+" -- tags
+command! -nargs=* -range GoAddTags call go#tags#Add(<line1>, <line2>, <count>, <f-args>)
+command! -nargs=* -range GoRemoveTags call go#tags#Remove(<line1>, <line2>, <count>, <f-args>)
+
 " -- tool
 command! -nargs=0 GoFiles echo go#tool#Files()
 command! -nargs=0 GoDeps echo go#tool#Deps()

plugin/go.vim

@@ -18,6 +18,7 @@ let s:packages = [
       \ "github.com/jstemmer/gotags",
       \ "github.com/klauspost/asmfmt/cmd/asmfmt",
       \ "github.com/fatih/motion",
+      \ "github.com/fatih/gomodifytags",
       \ "github.com/zmb3/gogetdoc",
       \ "github.com/josharian/impl",
       \ ]